• Human milk is recognized as the optimal nutrition for infants by the American Academy of Pediatrics (AAP), the World Health Organization (WHO), the Surgeon General, and all major medical groups.
  • Physiology
    • Breast milk production
      • Lactogenesis I: Milk production begins around 16 weeks prenatally.
      • Lactogenesis II: onset of copious milk secretion around 2 to 3 days after vaginal delivery; under hormonal control initiated by the expulsion of placenta and decrease in progesterone levels
      • Lactogenesis III: Mature milk production (maintenance) depends on autocrine (local) control. The amount of milk removed influences milk volume. If milk is not removed, a protein (feedback inhibitor of lactation) accumulates and inhibits prolactin release.
      • Prolactin is released from the anterior pituitary in response to nipple stimulation and triggers milk secretion into the lumen of breast alveoli.
      • Oxytocin is released from the posterior pituitary gland, causing ejection of milk into the breast ducts (milk ejection reflex).
      • Let-down can be triggered by physical stimulation of the breast or by mental stimulation such as hearing a baby cry.
    • Composition
      • Largely independent of maternal diet, except for fatty acids and water-soluble vitamins.
      • Colostrum contains high levels of secretory immunoglobulin A for immune protection. Lactoferrin stimulates meconium passage and promotes colonization with protective lactobacillus bifidus.
      • High whey-to-casein ratio
      • Milk changes within a feed and throughout the day. Hindmilk and milk at night contains higher fat and calories.



  • 81% of infants born in the United States in 2013 initiated breastfeeding, according to the Centers for Disease Control and Prevention.
  • At 3 months, 44% breastfed exclusively.
  • At 6 months, 52% breastfed, 22% exclusively
  • At 12 months, 31% breastfed.
  • Racial and economic disparities in breastfeeding exist; lower rates in the SE United States among African American women and women living in poverty

Risk Factors

  • Contraindications to breastfeeding:
    • Infant with classic galactosemia
    • Maternal conditions:
      • HIV (in industrialized countries)
      • Illicit drug use
      • Active, untreated tuberculosis
      • Herpes simplex virus lesions on breast
      • HTLV-I– or HTLV-II–positive
      • Exposure to radioactive material, while there is radioactivity in the milk
      • Use of some medications, such as cytotoxic drugs
  • Infant conditions that may interfere with breastfeeding:
    • Prematurity
    • Low birth weight
    • Hypotonia
    • Cleft lip or palate
    • Ankyloglossia (tongue-tie)
  • Maternal conditions that may interfere with breastfeeding:
    • History of breast surgery
    • Abnormal breast shape (glandular insufficiency)
    • Inverted nipples
    • Medications that inhibit lactation
    • Endocrine: infertility, hypothyroidism, polycystic ovary, retained placenta, Sheehan syndrome, obesity
  • Common reasons cited for early termination of breastfeeding:
    • Perceived insufficient milk supply
    • Poor latch
    • Sore nipples
    • Returning to work or school

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